Core Losses in Transformers

No formula to calculate, need the transformer to do the open circuit test. See the previous thread (http://cr4.globalspec.com/thread/37060) for how to do this test. If you want to do the test, provide 433 V to the secondary with primary terminals open and measure the power consumed. Do the test in a testing shop with qualified personnel and be careful about the induced high voltage (22 KV) of the secondary terminals.

- MS

The most practical and meaningful way is by measurement method.No load loss of distribution transformers consist of core loss,air gap loss and stray loss.Below is the varables that affect core losses of transformer if you are interested.

The bigger component is core loss which is the eddy current loss in the cold roll grain orientated silicon steel.To reduce the eddy current the thicknes of the lamination/magnetic steel plates that form the core must be reduced to the optimum thickness beyond which there is no significant advantage while the cost goes futher up.The other component is the magnetic flux losses due to air gaps at the 45 degree or poorer 90 degree joints of the yoke and the bracing of the stepped or straight core.This can be reduced by having very accurate cutting and stacking of core material.There is a small amout of stray loss which is left alone.The magnetising current,that is maintaining a flux desity of about 1.55 to1.65 Tesla in the transformer cores thus measured is used to calculate the no load loss at the particular room temperature.This figure is then corrected to say,losses at 75 degree celsus which is used for comparision of the losses of different manufacturers' products.For the same batch of transformers of the same rating,the losses can be slightly different.Specifying losses withot specifying temperature is meaningless.

Regards,

Khor